Usually, when a computer room of a data center or the like has a window, the computer room is likely to receive an influence of conduction heat from the outdoors in the summer season. Therefore, for the purpose of suppressing an influence of conduction heat from the outdoors in the summer season, for example, countermeasures of providing a shading curtain 51 on an indoor side of a window 3 as illustrated in FIG. 7, attaching a light shielding film on a window glass Japanese Patent Application Laid-Open Publication No. 2010-265622 and providing a double window have been taken.